[Android Q&A, Help & Troubleshooting] Kite-G:
Sorry for not responding earlier, been busy. Anyways, so this happened. i uninstalled the app and all its files, the img and everything, re-installed, downloaded the small img you linked (renamed folder to Ubuntu, its files too and the img name inside the md5), updated script within app, launched, after the first setup still gray screen, exit, installed the script to the one in your FAQ, carefully followed your instructions to install the scripts.tar.gz (thanks), used the line you said after i ran the app, and this happened:

u0_a80@roth:/ $
u0_a80@roth:/ $ cd /sdcard/ubuntu
u0_a80@roth:/sdcard/ubuntu $ su
root@roth:/ # /data/data/com.zpwebsites.linuxonandroid/files/start /sdcard/Ubuntu/ubuntu.img
uxonandroid/files/bootscript.sh /sdcard/ubuntu/ubuntu.img <
MD5 file found, use to check .img file? (y/n)
/data/data/com.zpwebsites.linuxonandroid/files/bootscript.sh[83]: [: /sdcard/Ubuntu/ubuntu.img: unexpected operator/operand
Checking loop device... MISSING
Creating loop device... OK
No user defined mount points
net.ipv4.ip_forward = 1
Config file not found, using defaults!(/root/cfg/ubuntu.img.config)
Starting first boot setup.......
chmod: cannot access `/dev/shm': No such file or directory
groupadd: group 'android_bt' already exists
groupadd: group 'android_bt-net' already exists
groupadd: group 'android_inet' already exists
groupadd: group 'android_net-raw' already exists
mkdir: cannot create directory `/var/run/dbus': File exists

Now give your user account (named ubuntu) a password

Please enter the new password below

passwd: u:r:init:s0 is not authorized to change the password of ubuntu
chown: cannot access `/external-sd/': No such file or directory
groupadd: group 'sdcard-rw' already exists
Start VNC server? (y/n)
y
Start SSH server? (y/n)
y
Now enter the screen size you want in pixels (e.g. 800x480), followed by [ENTER]:
1280x720

New 'X' desktop is localhost:0

Starting applications specified in /home/ubuntu/.vnc/xstartup
Log file is /home/ubuntu/.vnc/localhost:0.log

If you see the message 'New 'X' Desktop is localhost:0' then you are ready to VNC into your ubuntu OS..

If connection from a different machine on the same network as the android device use the address below:
eth0: error fetching interface information: Device not found

If using androidVNC, change the 'Color Format' setting to 24-bit colour, and once you've VNC'd in, change the 'input mode' to touchpad (in settings)
* Starting OpenBSD Secure Shell server sshd [ OK ]
Save settings as defaults? (y/n) (You can always change it later in the app)
y
Config saved to /root/cfg/ubuntu.img.config

To shut down the Linux environment, just enter 'exit' at this terminal - and WAIT for all shutdown routines to finish!

root@localhost:~#

It started fine i think, though it skipped the password part and didnt allow me to check md5 (had checked it manually so no problem), still gray screen.

Exit everything and launched again, terminal returned this:

u0_a80@roth:/ $
u0_a80@roth:/ $ cd /sdcard/ubuntu
u0_a80@roth:/sdcard/ubuntu $ su
root@roth:/ # /data/data/com.zpwebsites.linuxonandroid/files/start /sdcard/Ubuntu/ubuntu.img
PATH=/data/data/com.zpwebsites.linuxonandroid/files:/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin
ash: can't open 'bootscript.sh'
2|root@roth:/ #

After this i somehow decided to restore my device to stock with a factory image (wiped completely everything, but staying on 4.3), then installed everything again, exact same order and procedure as earlier when i uninstalled everything to try again. But this time, upon launching Ubuntu from the app, Ubuntu started by itself, didn't stop at line 4 like usual, installed your script, the scripts.tar.gz too, and ran again. Didn't had to input the /data/data/..../file/start line, because it started by itself again:

u0_a84@roth:/ $
u0_a84@roth:/ $ cd /sdcard/ubuntu
u0_a84@roth:/sdcard/ubuntu $ su
sh /data/data/com.zpwebsites.linuxonandroid/files/bootscript.sh /sdcard/ubuntu/ubuntu.img
sh /data/data/com.zpwebsites.linuxonandroid/files/bootscript.sh /sdcard/ubuntu/ubuntu.img
inuxonandroid/files/bootscript.sh /sdcard/ubuntu/ubuntu.img <
MD5 file found, use to check .img file? (y/n)
n
Checking loop device... FOUND
No user defined mount points
net.ipv4.ip_forward = 1
Using config file /root/cfg/ubuntu.img.config
Config file loaded

New 'X' desktop is localhost:0

Starting applications specified in /home/ubuntu/.vnc/xstartup
Log file is /home/ubuntu/.vnc/localhost:0.log

If you see the message 'New 'X' Desktop is localhost:0' then you are ready to VNC into your ubuntu OS..

If connection from a different machine on the same network as the android device use the address below:
eth0: error fetching interface information: Device not found

If using androidVNC, change the 'Color Format' setting to 24-bit colour, and once you've VNC'd in, change the 'input mode' to touchpad (in settings)
* Starting OpenBSD Secure Shell server sshd [ OK ]
To shut down the Linux environment, just enter 'exit' at this terminal - and WAIT for all shutdown routines to finish!

root@localhost:/#

Opened VNC, and to my surprise, it worked. Even checking md5 in the setup worked, unlike before. Downloaded the large img and it worked too. So i guess it was a problem with either my ROM or my previous img, not sure. Either way thanks for all your help, greatly appreciated. :)